Properties of Spinel Protective Coatings Prepared Using Wet Powder Spraying for SOFC Interconnects

Manganese cobalt spinel coatings have attracted much interest as a protective layer for stainless steel interconnects of solid oxide fuel cells (SOFCs) owing to their effectiveness of suppressing high temperature oxidation and Cr evaporation. In this study, a simple wet powder spraying (WPS) method was applied to prepare spinel layers on commercial stainless steels (Sanergy HT and K41/441) which were evaluated as protective coating of SOFC interconnects. A condition of heat treatment on spray coatings was optimised to achieve dense protective layers with microstructure analysis. Area specific resistance (ASR) and stability were measured in a humid atmosphere at 700 °C for 1000 hours. Post-test analysis was conducted on microstructure of measured samples using SEM-EDS. In addition, effect of a sublayer with spinel coatings was investigated on ASR and Cr retention. The implication for microstructure, ASR and stability of the evaluated coatings is discussed.